Understanding the mechanisms by which chemical compounds and drugs interact with both the aryl hydrocarbon receptor (AhR) and estrogen receptor (ER) signaling pathways is important both for identifying potential environmental and endocrine disruptors and for screening compounds for therapeutic use. The existence of cross-talk between AhR and ER causes certain AhR ligands to exert estrogenic endocrine disrupting activity in the absence of binding to ER. Existing methods for studying these mechanisms are cumbersome and time consuming, and for cell-based methods, compound degradation by cellular metabolism significantly affects results. Recently, IA has developed biosensors for studying real-time association and dissociation kinetics between ER-alpha & -beta, and estrogenic nuclear response element (ERE) in the presence of agonists and antagonists. IA proposes to extend this technology to develop chemistries and methods which will allow the biosensors to be applied to study the complex AhR-mediated signaling pathways. During Phase I, biosensors for assessing the interaction of AhR with ligands, accessory proteins, and dioxin response element (DRE) will be developed. During Phase II, biosensors will be used to analyze cross-talk between ER and AhR, and to create screening methods for predicting effects of compounds based on hER & AhR mechanisms. PROPOSED COMMERCIAL APPLICATIONS: Biosensors which allow studying the real-time binding kinetics of compounds (agonists, antagonists, accessory proteins) to the AhR will provide researchers with powerful tools for screening environmental endocrine disruptors and for designing, developing, and testing new pharmaceuticals for treatment of cancer.